It is well known to provide various types of packages with a reclosable profile strip or zipper for releasably securing the contents of the package. Such packages may be used to store a variety of items such as food products or other non-food hardware articles. A typical design for the reclosable mechanism of a profile strip is described in the patent to Naito, U.S. Pat. No. 3,198,228. Naito discloses occludent or interlocking means comprising a rib or male closure member and a mating groove or female closure member, formed along the inside of the open end of a package with the two members facing each other. The male and female members can be interlocked and disengaged under pressure, forming a pressure fastenable and releasable closure mechanism. Naito also discloses the provision of a pair of supporting rails attached to the male member with one post positioned on each side of the male member.
In some applications the profile strips are formed integrally with the package material while in other applications the profile strips are formed separately and sealed to the package. In either case the strips are completely attached to the package.
One common approach to the design of the interlocking closure mechanism has been to provide a device which requires different forces to disengage the mechanism depending on the origin of the force. Disengagement forces will originate from either the inboard side (package side) of the closure mechanism, such as those forces exerted by the contents of the package either at rest or from falling, tumbling or shock, or from the outboard side of the closure mechanism as would be exerted by a person attempting to get into the package. These devices are designed such that the force required to open the interlocking closure mechanism from the inboard side is greater than the force required to open the mechanism from the outboard side. Examples of such designs are disclosed in the patents to Naito U.S. Pat. No. 3,198,228 and Ausnit U.S. Pat. No. 4,736,451. It has been found that these designs lend themselves to being opened inadvertently due to the small force required to open the interlocking closure mechanism from the outboard side.
A different and less common approach to the design of the interlocking closure mechanism has been to design a device in view of the psychology of the average user. The user tends to be skeptical of an interlocking closure mechanism which can be easily opened from the outboard side because she or he fears that such a mechanism will present an insufficient resistance to a force which acts from the inboard side. Thus, interlocking closure mechanisms have been designed which require the same amount of force to disengage the mechanism from the outboard side as from the inboard side. An example of such a design is disclosed in the patent to Siegel, U.S. Pat. No. 3,633,642. It has been found that an acceptable range of interlocking forces exist which are both strong enough to contain or maintain the contents of the package and at the same time not so strong as to cause the user too much difficulty in getting into the package.
It is an object of the present invention to provide an improved design for a reclosable profile strip that is in keeping with the objectives of the later less common approach. Hence, it is an object of the present invention to provide an improved design for a profile strip which requires a single amount of force for disengagement and is less susceptible to inadvertent opening. To these ends the present invention provides a limited path for disengaging forces to act upon the profile, regardless of whether those forces originate on the outboard or inboard side. Thus there is a single minimum amount of force required to disengage the profile strips and open the package from the inboard or outboard side. Only one disengagement motion is contemplated for the profile strip and thus only one resistance to the disengagement need be provided. The invention eliminates the problem of inadvertent opening from the outboard side and is more consistent with the psychology of the user as described above. The need for only one method of resistance to disengagement simplifies the design and requires less material.